The Berkeley Center for Structural Biology (BCSB) operates five macromolecular crystallography beamlines at the Advanced Light Source, and is now building a new microfocus beamline, Gemini. The new beamline will provide an order of magnitude higher flux than the current beamlines, in a user- focusable beam down to 10 microns. Gemini is being built to address the current need for high- brightness small-beam crystallography in the country; the current microfocus beamlines are oversubscribed, and demand far outstrips capacity. With Gemini, we aim to alleviate this need by supplying a state-of-the-art structural biology tool for NIH-funded investigators around the country. While Gemini will use the most state-of-the art automation, software processing, and hardware control, it as yet does not have funding for a high-end detector system to match the other capabilities of the beamline. Detectors based on pixel-arrays for direct photon counting have made huge advances in the last few years, and have become increasingly common at national user facilities. The gain in speed, quantum efficiency, sensitivity, and dynamic range of these systems over most current CCD detectors is significant, and in fact critical to the success of many structural biology projects. The high speed enables fine phi slicing mode of data collection while minimizing radiation damage, and allows extremely high throughput so that many more samples can be analyzed. The large dynamic ranges means that both strong and weak reflections can be collected simultaneously, which also minimizes radiation damage and increases throughput. The fact that a reflection can be captured on a single pixel, due to the very small point spread function, effectively reduces spot size on the detector. Our goal is to install a high-end pixel-array detector on Gemini, which will have over 75% of its time available to serve NIH-supported researchers.